Light dependent magnetoreception in birds: the effect of intensity of 565-nm green light

In a previous study, Australian silvereyes tested in autumn under monochrom atic 565-nm green light at intensities of 2.1 and 7.5 mW m(-2) preferred th eir normal northerly migratory direction, whereas they showed a significant ly different tendency towards northwest at 15.0 mW m(-2). Repeating these e xperiments in spring with silvereyes migrating southward, we again observed well-oriented tendencies in the migratory direction at 2.1 and 7.5 mW m(-2 ). At 15.0 mW m(-2), however, the birds once more preferred northwesterly d irections, i.e. their response under this condition proved to be independen t of the migratory direction. This contradicts the interpretation that mono chromatic green light of this high intensity leads to a rotation of compass information; instead, it appears to produce sensory input that causes bird s to give up their migratory direction in favor of a fixed direction of as yet unknown origin.